Major electric appliances traditionally have been powered almost exclusively by alternating current (AC) inputs from a utility provider (for North America residential this being standard wall plug 120V and 240V AC lines).
Recently and independently, interest in “smart appliances” has paralleled the growing interest in the concept of a “smart grid”, in which communications and data about various elements of a power grid can be used to better monitor and in some cases modulate the power usage.
For recent smart appliance efforts, a major residential appliance such as a refrigerator, washer or dryer, water heater or possibly other appliance may incorporate more efficient operation, as well as some level of 1-way or 2-way signaling or communication, allowing the user and/or the utility electricity provider to view or measure power consumption and other data related to the appliance operation, and in some cases communicate back to the appliance to modulate its power usage during identified periods where reducing the load on a utility or other electricity grid is deemed beneficial. This ability to signal an electricity-consuming device to lower (or delay) its current power consumption is referred to often as “Demand Response” (DR). DR time is identified generally as either times of peak rates, when reducing or delaying loads has a monetary benefit for the consumer, or as times of peak utility loads, when reducing or delaying loads lessens the burden on the grid and therefore has direct and indirect benefits for the power provider.
One known problem in successfully utilizing these schemes in relation to residential devices is that consumers may choose to opt out of actions which compromise the operation of their lifestyle products, such as allowing a refrigerator to delay defrost cycles or increase temperature, or delaying washing or drying cycles. Thus challenges exist in predicting the amount of energy conserved by a large scale implementation of DR technologies.
Another problem is in achieving the maximum desired impact on temporary energy savings from conventional appliances. Even smart appliances (devices achieved by adding communication and increasing efficiency) only “reduce” the power consumption but do not “eliminate” power consumption on the grid during DR periods. These devices are also dependent on the consumers' willingness to compromise the full operation of the appliance and the individual consumer's usage habits. In this case, ambient household temperature, refrigerator duty cycle and food content, and specific usage cycles of washing machines, hot water applications such as showers and baths, are all difficult to accurately predict, and thus even smart appliances face a further issue of variable and difficulty in quantify energy savings. Thus, conventional DR systems face an inherent limitation on the state of energy use and degree of energy savings which may be predictably achieved.
Another aspect of this same “smart home”/“smart grid” evolving vision involves energy storage. To date, energy storage with regards to home use has been almost entirely limited to mobile devices (remote controls, small vacuum cleaners, power tools, and even small televisions among others). Peripherally, a category of back-up power supplies commonly referred to as Uninterruptable Power Supplies (UPS) has existed for providing back-up AC power (when an inverter is included to generate AC voltages), and more recently models of generalized energy storage including Community Energy Storage (for example metal housings the size of a small car secured within a neighborhood holding 1-100 KWH class storage devices such as batteries), or even residential level general purpose energy storage solutions (for example server rack style cases populated with high-capacity storage devices such as batteries). In each case, the costs of efficient, high-energy density battery technologies has proven an obstacle to large scale adoption, and perhaps just as much a problem is the market challenges of implementing battery-centric solutions which require even larger up-front costs as well as require new sales channels and value propositions to justify this new large apparatus being purchased for its own merits. The benefits in each case might make intellectual sense, but the method of implementing these storage solutions to date has proven limited, particularly at a residential level.